World's Heaviest Insect Makes Remarkable Comeback After Conservation Efforts

The wētāpunga, recognized as the world's heaviest insect, has staged a significant comeback, recovering from the verge of extinction due to dedicated conservation initiatives. An adult female wētāpunga can reach the weight of a mouse, grow up to four inches (10 cm) long, and possess a leg span of up to eight inches (20 cm).

These large, nocturnal, plant-eating insects were once widespread across New Zealand's North Island. However, the introduction of invasive predators like cats and stoats, coupled with habitat loss, led to a dramatic decline in their numbers. By the 1990s, the wētāpunga was officially declared endangered, and its population was reduced to a handful of individuals on a single island in the Hauraki Gulf, presumed extinct on the mainland.

Following the successful eradication of rats from this island, the wētāpunga population began a slow recovery, increasing from 78 in 2005 to 172 in 2009. Concerned that this growth was insufficient, conservationists launched an extensive breeding program.

Beginning in 2008, researchers collected six breeding-age wētāpunga and initiated an 'ex situ' breeding program at facilities including Butterfly Creek and Auckland Zoo. Over the past 15 years, this program has bred and released approximately 11,000 wētāpunga into the wild across 10 specially selected predator-free sites around New Zealand. These sites include eight islands and two fenced nature reserves in the North Auckland region.

As breeding techniques improved and the captive population grew, the researchers scaled up production, eventually rearing tens of thousands of young wētāpunga, known as nymphs. These nymphs are cared for in communal creches until they are large enough for individual cages or release into the wild. Their diet includes fresh greens, leaf litter, and fish flakes for essential protein, a critical factor in their survival.

Intensive monitoring of the released populations has yielded promising results. On Motuora and Tiritiri Matangi islands, wētāpunga have now established self-sustaining populations, with at least four generations born in the wild. This success indicates that the conservation efforts have enabled the species to establish viable populations.

As a result of these conservation successes, the wētāpunga's status has been upgraded from 'nationally endangered' to 'nationally increasing.' Dr. Chris Green, an honorary researcher at the Department of Conservation and lead author of a study on the release program, expressed optimism for the species' future, stating, 'The future of wētāpunga is looking bright.'

Researchers hope that the methodologies developed to save the wētāpunga can be applied to protect other threatened species in New Zealand, including the Canterbury knobbled weevil and several native stag beetle species. The findings of this conservation effort were published in the New Zealand Journal of Zoology.